Odorless or low-odor crosslinkable compound and resin composition containing the same

ABSTRACT

A crosslinkable compound obtained by reacting an aromatic hydrocarbon-formaldehyde resin with an α,β-unsaturated monocarboxylic acid or an ester thereof has no odor or very slight odor. Said crosslinkable compound can be radical polymerized at a low temperature to give a cured article having excellent electrical insulating properties. Said crosslinkable compound can also be used as one component of a resin composition containing an unsaturated polyester resin or a polybutadiene resin modified with acrylic or methacrylic acid to give an odorless or low-odor resin composition suitable for producing reinforced plastics, paints and varnishes, adhesives, electrical parts, etc.

BACKGROUND OF THE INVENTION

This invention relates to an odorless or low-odor crosslinkable compoundand an odorless or low-odor resin composition containing the same. Moreparticularly, this invention relates to an odorless or low-odorcrosslinkable compound obtained by reacting an aromatichydrocarbon-formaldehyde resin with an α,β-unsaturated monocarboxylicacid or its ester and an odorless or low-odor resin compositioncontaining the crosslinkable compound.

Aromatic hydrocarbon-formaldehyde resins have been studied, for example,by A. J. Baeyer in the latter half of the 19th century and resinousproducts have been obtained by reacting an aromatic hydrocarbon such asbenzene, toluene, xylene, mesitylene, durene, naphthalene, acenaphthene,or the like with formaldehyde in the presence of a strong acid catalyst(A. J. Baeyer; Ber., vol. 5, p. 1098 (1872), ibid., vol. 6, p. 223(1873) and ibid., vol. 7, p. 1190 (1874)). Further, new knowledge as tocondensation reaction of an aromatic hydrocarbon and formaldehyde wasfound by R. Wegler during the Second World War and the foundationthereof has been established (R. Wegler; Angew. Chem. A/60, No. 4, p. 88(1948)).

In Japan, M. Imoto, K. Fu, and others have widely studied aromatichydrocarbon-formaldehyde resins after the Second World War and givenfoundation of development, so that aromatic hydrocarbon-formaldehyderesins such as xylene-formaldehyde resin, and the like are manufacturedindustrially.

As is well known in the art, aromatic hydrocarbon-formaldehyde resinsare generally viscous liquid and excellent in adhesive properties, waterresistance, humidity resistance, acid resistance, alkali resistance, andelectrical insulating properties. But when electrical insulatingmaterials are obtained by condensation reaction with phenols, amines, orthe like at high temperatures in the presence of an acid catalyst byapplying reactivity of the methylol group, ether linkage and acetallinkage in the resin, there are many disadvantages in that water isby-produced by the condensation reaction, high temperatures arenecessary for completing the reaction, and the like. In addition,low-molecular weight polymers such as prepolymers usually have an odor.When they are cured, a more offensive odor is emitted, which is notpreferable from the viewpoint of health of the workers and residentstherearound. Such a problem should also be solved.

On the other hand, since unsaturated polyester varnishes are relativelybalanced in mechanical and electrical properties, heat resistance,workability, and production cost, they have been used in large amountsin glass fiber reinforced plastics, paints and varnishes, adhesives,electrical parts, and the like. Unsaturated polyester varnishes comprisemainly unsaturated polyester resin and a crosslinkable monomer which isusually contained in an amount of 40 to 60% by weight. As thecrosslinkable monomer, a relatively low-molecular weight compound suchas styrene has been used from the viewpoint of properties or economy.But since the compound has a low molecular weight and is very volatile,there are many disadvantages in that the weight of the varnish is lostin an amount of 20 to 60% by weight by vaporization in the state ofvarnish and at the time of curing, an irritating odor is emitted and isnot preferable from the viewpoint of health of the workers and residentstherearound, and the like.

SUMMARY OF THE INVENTION

It is an object of this invention to provide an orderless or low-odorcrosslinkable compound which can be radical polymerized at a lowtemperature. It is another object of this invention to provide a polymerobtained from said crosslinkable compound. It is a further object ofthis invention to provide an odorless or low-odor resin compositioncontaining said crosslinkable compound overcoming the disadvantages ofconventional unsaturated polyester varnishes mentioned above.

This invention provides an odorless or low-odor crosslinkable compoundobtained by reacting an aromatic hydrocarbon-formaldehyde resin with anα,β-unsaturated monocarboxylic acid or an ester thereof.

This invention also provides a polymer of odorless or low-odorcrosslinkable compound obtained by reacting an aromatichydrocarbon-formaldehyde resin with an α,β-unsaturated monocarboxylicacid or an ester thereof.

This invention further provides an odorless or low-odor resincomposition comprising.

(A) an unsaturated polyester resin or a polybutadiene resin modifiedwith acrylic acid or methacrylic acid, and

(B) a crosslinkable compound obtained by reacting an aromatichydrocarbon-formaldehyde resin with an α,β-unsaturated monocarboxylicacid or an ester thereof.

This invention still further provides a polymer of said crosslinkablecompound and a process for the production thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a test piece and

FIG. 2 is a cross-sectional view of the test piece taken along lineII--II of FIG. 1, for measuring adhesive strength under shear.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The aromatic hydrocarbon-formaldehyde resin used in this invention as astarting material can be obtained by condensation reaction of anaromatic hydrocarbon with formaldehyde by a conventional process.Examples of the aromatic hydrocarbon-formaldehyde resins arexylene-formaldehyde resin, toluene-formaldehyde resin,mesitylene-formaldehyde resin, durene-formaldehyde resin,naphthalene-formaldehyde resin, and the like.

Examples of the α,β-unsaturated monocarboxylic acids and their estersare acrylic acid, methacrylic acid, α-chloroacrylic acid, crotonic acidand their alkyl esters, the alkyl moiety having 1 to 4 carbon atoms,e.g. methyl acrylate, methyl methacrylate, ethyl acrylate, ethylmethacrylate, propyl acrylate, propyl methacrylate, butyl acrylate,butyl methacrylate, etc. These compounds may be used alone or as amixture thereof.

The reaction of the aromatic hydrocarbon-formaldehyde resin with theα,β-unsaturated monocarboxylic acid or its ester can be carried out withheating, if required, by using a conventional esterification catalyst,an ester interchange catalyst, a polymerization inhibitor, and the like.In the reaction, a desired amount of the unsaturated monocarboxylic acidgroup (e.g. acrylic acid group or methacrylic acid group) can beintroduced into the crosslinkable compound by changing the reactionconditions such as changing the amount of the α,β-unsaturatedmonocarboxylic acid or its ester. Further, a viscosity of the resultingcrosslinkable compound can be adjusted desirably by changing themolecular weight of the aromatic hydrocarbon-formaldehyde resin. Asmentioned above, it is possible to give various kinds of crosslinkablecompounds by changing the reaction conditions such as the kind and useamount of the aromatic hydrocarbon-formaldehyde resin and/orα,β-unsaturated monocarboxylic acid or its ester, reaction time andreaction temperature. More concretely, the crosslinkable compound havingdesirable properties can be obtained by using preferably 10 to 200 partsby weight, more preferably 30 to 110 parts by weight, of theα,β-unsaturated monocarboxylic acid or its ester based on 100 parts byweight of the aromatic hydrocarbon-formaldehyde resin, and heatingpreferably at a temperature of 80° to 130° C., more preferably refluxingat a temperature of 100° to 130° C.

The ester linkage derived from the reaction of the aromatichydrocarbon-formaldehyde resin with the α,β-unsaturated monocarboxylicacid or its ester can be identified in the resulting crosslinkablecompound by infrared absorption spectra. The crosslinkable compound hasno odor or a very slight odor and can be polymerized by radicalpolymerization at a low temperature. A cured article can be formed fromthe crosslinkable compound at a temperature of preferably from roomtemperature to 180° C., more preferably from 60° to 130° C. forpreferably from 10 minutes to 20 hours, more preferably from 1 to 15hours, by using a curing agent in an amount of preferably 0.1 to 5% byweight, more preferably 1 to 30% by weight together with a curingaccelerator in an amount of preferably 0 to 2% by weight based on theweight of the crosslinkable compound. The resulting cured article isexcellent in electrical insulating properties. In order to form curedarticles from the crosslinkable compound, there can also be used one ormore crosslinkable monomers, polymerization inhibitors, fillers, and thelike additives together with the curing agent and the curingaccelerator, examples of these catalyst and additives being explained indetail hereinafter as to the odorless or low-odor resin composition.

Further the crosslinkable compound is very useful as a crosslinkingagent for unsaturated polyester resins or polybutadiene resins modifiedwith acrylic acid or methacrylic acid and is superior to theconventional crosslinkable monomers in smallness in loss of weight onvolatilization. Thus, there is provided the odorless or low-odor resincomposition comprising (A) an unsaturated polyester resin or apolybutadiene resin modified with acrylic acid or methacrylic acid and(B) the crosslinkable compound obtained by reacting an aromatichydrocarbon-formaldehyde resin with an α,β-unsaturated monocarboxylicacid or an ester thereof, preferably in an amount of 20 to 100 parts byweight of (B) per 100 parts by weight of (A).

As the unsaturated polyester resin used as the component (A), there canbe used various general-purpose unsaturated polyester resins obtainedfrom the alcohol component, the acid component, and if necessary themodifying component mentioned below.

(1) ALCOHOL COMPONENT

Aliphatic glycols such as ethylene glycol, propylene glycol, diethyleneglycol, dipropylene glycol, triethylene glycol, 1,3-propanediol,1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol,1,2-pentanediol, 1,3-pentanediol, 1,2-hexanediol, 1,4-hexanediol,2,3-hexanediol, dipropylene glycol, and the like; alicyclic diols suchas cyclopentanediol, cyclohexanediol, and the like; aromatic diols suchas xylene glycol, dimethylxylene glycol,2,2-bis(4-hydroxyphenyl)propane, and the like; ethers such asbis(2-hydroxyethyl)ether, bis(3-hydroxy propyl)ether, bis(4-hydroxybutyl)ether, and the like; polyhydric alcohols such as glycerin,trimethylolethane, trimethylolopropane, pentaerythritol, and the like;or a mixture thereof.

The above-mentioned alcohols are generally produced industrially andused for producing unsaturated polyesters.

(2) ACID COMPONENT

Unsaturated carboxylic acids such as maleic acid, maleic anhydride,fumaric acid, itaconic acid, citraconic acid,endomethylene-tetrahydrophthalic anhydride, methyltetrahydrophthalicanhydride, and the like; vegetable oil fatty acids such as those fromlinseed oil, soybean oil, tall oil, coconut oil, castor oil, and thelike; or derivatives thereof or a mixture thereof.

Saturated acids such as phthalic acid, phthalic anhydride, isophthalicacid, terephthalic acid, adipic acid, and the like can be used, ifdesired, together with the acid component mentioned above.

(3) MODIFYING COMPONENT (OPTIONAL COMPONENT)

Cyclopentadiene, dicyclopentadiene, and the like.

As the polybutadiene resin modified with acrylic acid or methacrylicacid which is an alternative member of the component (A), there can beused polybutadienes having reactive double bonds at the terminalsobtained by introducing active groups such as epoxy groups, hydroxylgroups, carboxyl groups, urethane groups, etc. at the terminals ofpolybutadienes and reacting said active groups with the carboxyl groupof acrylic acid or methacrylic acid. Examples of the modifiedpolybutadienes are a polybutadiene modified with methacrylic acid, e.g.TE-2000 (manufactured by Nippon Soda Co., Ltd., Japan), a polybutadienemodified with acrylic acid, e.g. VTB 2000×164, VTBN 1300×22, VTBNX1300×23 (manufactured by Ube Industries, Ltd.), and the like.

The odorless or low-odor resin composition of this invention may furthercontain one or more curing agents, curing accelerators, crosslinkablemonomers, modifying resins, polymerization inhibitors, fillers and thelike.

As the curing agents, there can be used acyl peroxides such as benzoylperoxide, acetyl peroxide, etc.; hydroperoxides such as t-butylhydroperoxide, cumene hydroperoxide, etc.; ketone peroxides such asmethy ethyl ketone peroxide, cyclohexanone peroxide, etc.; dialkylperoxides such as di-t-butyl peroxide, dicumyl peroxide; etc.;oxyperoxides such as t-butyl perbenzoate, t-butyl peroxyacetate, etc.

The curing agents may generally be used in an amount of 0.5 to 5% byweight, preferably 1 to 3% by weight based on the weight of resincomposition.

As the curing accelerators, conventional metal (e.g. Co, Mn, Fe, Pb, Ni,Sn, Zn, or the like) salts of naphthenates or octoates can be used in anamount of up to 2.0% by weight based on the weight of the resincomposition.

As the crosslinkable monomers, there can be used general-purposecrosslinkable monomers for unsaturated polyesters such as styrene,various esters of acrylic acid or methacrylic acid having high boilingpoints, high-boiling point allyl ethers, e.g. trimethylolpropane allylether, glycerin allyl ether, diallyl phthalate, diallyl isophthalate,triallyl isocyanurate, etc. These crosslinkable monomers are used asoccasion demands.

As the modifying resins, saturated polyester resins, variouspolybutadiene resins, and the like may be used, if required.

As the polymerization inhibitors, conventional ones such as quinones,e.g. hydroquinone, p-t-butyl catechol, pyrogallol, and the like may beused in an amount of 0 to 0.5% by weight based on the weight of theresin composition.

As the fillers, there can be used those used for polyester resins suchas silica, talc, calcium carbonate, asbestos, glass fibers, woodmeal,and the like, if required, with or without colorants.

This invention is illustrated more particularly by way of the followingexamples, in which all percents are by weight unless otherwisespecified.

EXAMPLE 1 PRODUCTION OF CROSSLINKABLE COMPOUND (A)

In a 3-liter four-necked flask equipped with a stirrer, a thermometer,an Allihn condenser, 800 g of xylene-formaldehyde resin (Nikanol LLLmanufactured by Mitsubishi Gas Chemical Co., Inc., average molecularweight 330-350), 250 g of methacrylic acid, 1 g of t-butyl catechol and3 g of p-toluenesulfonic acid were placed and reacted at 100° C. for 8hours. The reaction product was dissolved in 1 liter of benzene andwashed with 500 ml of an aqueous solution of about 10% sodium carbonatefollowed by washing with distilled water. After removing water from theorganic layer over anhydrous sodium sulfate, the benzene was removed bydistillation to give 720 g of crosslinkable compound (A).

The crosslinkable compound (A) had almost no odor and a viscosity of 1.2poises (at 25° C.). The crosslinkable compound (A) showed strongabsorption at 1720 cm⁻¹ due to the carbonyl group of the methacrylicacid ester when measured infrared absorption spectra. Further, thecrosslinkable compound (A) had 0.5 equivalent of the unsaturated bondper 100 g of the crosslinkable compound (A) when measured by thepyridine sulfate dibromide method.

EXAMPLE 2 PRODUCTION OF CROSSLINKABLE COMPOUND (B)

In a 3-liter four-necked flask equipped with a stirrer, a thermometer,and an Allihn condenser, 800 g of Nikanol LLL, 160 g of methacrylicacid, 1 g of t-butyl catechol and 2 g of p-toluenesulfonic acid wereplaced and reacted at 100° C. for 8 hours. After the completion of thereaction, the acid component was removed by using an ion exchange resinto give 700 g of crosslinkable compound (B).

The crosslinkable compound (B) had almost no odor and a viscosity of 1.6poises (at 25° C.). The crosslinkable compound (B) showed strongabsorption at 1720 cm⁻¹ due to the carbonyl group of the methacrylicacid ester in infrared absorption spectra and had 0.5 equivalent of theunsaturated bond per 100 g of the crosslinkable compound (B) whenmeasured by the pyridine sulfate dibromide method.

EXAMPLE 3 PRODUCTION OF CROSSLINKING COMPOUND (C)

The process of Example 1 was repeated except for using Nikanol LL(xylene-formaldehyde resin having an average molecular weight of 350-380manufactured by Mitsubishi Gas Chemical Company, Inc.) in place ofNikanol LLL to give crosslinkable compound (C) having almost no odor inan amount of 760 g.

The crosslinkable compound (C) showed strong absorption at 1720 cm⁻¹ dueto the carbonyl group of the methacrylic acid ester in infraredabsorption spectra.

EXAMPLE 4 PRODUCTION OF CROSSLINKABLE COMPOUND (D)

The process of Example 1 was repeated except for using Nikanol HH(xylene-formaldehyde resin having an average molecular weight of 500-600manufactured by Mitsubishi Gas Chemical Co., Inc.) in place of NikanolLLL to give 750 g of crosslinkable compound (D) having almost no odor.

The crosslinkable compound (D) showed strong absorption at 1720 cm⁻¹ dueto the carbonyl group of the methacrylic acid ester in infraredabsorption spectra.

EXAMPLE 5 PRODUCTION OF CROSSLINKABLE COMPOUND (E)

The process of Example 1 was repeated except for using 200 g of methylmethacrylate in place of methacrylic acid to give 730 g of crosslinkablecompound (E) having almost no odor.

The crosslinkable compound (E) showed strong absorption at 1720 cm⁻¹ dueto the carbonyl group of the methacrylic acid ester in infraredabsorption spectra.

EXAMPLE 6 PRODUCTION OF CROSSLINKABLE COMPOUND (F)

The process of Example 2 was repeated except for using acrylic acid inplace of methacrylic acid and protecting the flask from light to give730 g of crosslinkable compound (F) having almost no odor.

EXAMPLE 7

To each crosslinkable compound (A) to (F) obtained in Examples 1 to 6,0.5% of PT-28 (a solution of cobalt naphthenate manufactured by HitachiChemical Co., Ltd.) and 1.0% of CT-3 (t-butyl perbenzoate manufacturedby Hitachi Chemical Co., Ltd.) were added and gelation took place inabout 20 minutes. After maintaining at 100° C. for 1 hour, electricalproperties of cured articles of the crosslinkable compounds (A) to (F)were measured with the results as shown in Table 1.

                  TABLE 1                                                         ______________________________________                                        Insulation resistance                                                         (original state)    6-9 × 10.sup.16 ohms                                Insulation resistance                                                         (after boiling)     4-7 × 10.sup.15 ohms                                Dielectric constant 20° C.                                             (50 Hz)             3-4                                                       Dielectric loss tangent                                                       (tan δ) 70° C.                                                                       1-2%                                                      Dielectric loss tangent                                                       (tan δ) 20° C.                                                                       2-4%                                                      Dielectric strength 16 kV/mm or more                                          ______________________________________                                    

As is clear from Table 1, the crosslinkable compounds of this inventionshow excellent electric insulating properties, particularly great inboiling-resistant insulating properties.

The crosslinkable compound of this invention can be radial polymerizedat a low temperature and has no or very slight odor as mentioned above.Since cured articles of the crosslinkable compounds of this inventionare excellent in electrical insulating properties, particularlyelectrical insulating properties after boiling, that is,boiling-resistant insulating properties, they are very useful asinsulating materials in areas with high humidity like Japan.

EXAMPLE 8 PRODUCTION OF CROSSLINKABLE COMPOUND (G)

In a 1-liter four-necked flask equipped with a stirrer, a thermometer,and an Allihn condenser, 500 g of Nikanol LL, 125 g of methacrylic acid,0.5 g of hydroquinone, and 0.5 g of p-toluenesulfonic acid were placedand reacted at 120° C. for 8 hours. The reaction product was dissolvedin 1 liter of toluene, and washed with 500 ml of an aqueous solution ofabout 25% sodium carbonate three times followed by washing withdistilled water. After removing water from the organic layer withcalcium chloride, the toluene was removed by distillation to give 450 gof crosslinkable compound (G) having a viscosity of 1 poise (at 25° C.).

The crosslinkable compound (G) had almost no odor and showed strongabsorption at 1720 cm³¹ 1 due to the carbonyl group of the methacrylicacid ester in infrared absorption spectra.

EXAMPLE 9 PRODUCTION OF CROSSLINKABLE COMPOUND (H)

In the same flask as used in Example 8, 500 g of Nikanol LL, 150 g ofmethyl methacrylate, 0.5 g of hydroquinone, and 0.5 g ofp-toluenesulfonic acid were placed and reacted at 120° C. for 10 hours.After completion of the reaction, the reaction product was dissolved in1 liter of toluene and washed with an aqueous solution of about 25% ofsodium carbonate and distilled water in this order. After removing waterfrom the organic layer with calcium chloride, the toluene was removed bydistillation under reduced pressure of 5 mm Hg at 40° C. to give 400 gof crosslinkable compound (H) having a viscosity of 1 poise (at 25° C.).

The crosslinkable compound (H) had almost no odor and showed strongabsorption at 1720 cm⁻¹ due to the carbonyl group of the methacrylicacid ester in infrared absorption spectra.

EXAMPLE 10 PRODUCTION OF CROSSLINKABLE COMPOUND (I)

The process of Example 8 was repeated except for using Nikanol HH inplace of Nikanol LL to give 460 g of crosslinkable compound (I) havingalmost no odor.

EXAMPLE 11 PRODUCTION OF CROSSLINKABLE COMPOUND (J)

The process of Example 8 was repeated except for changing the reactiontemperature to 150° C., the reaction time to 30 hours, and the amount ofmethacrylic acid to 200 g to give 480 g of crosslinkable compound (J)having almost no odor.

EXAMPLE 12

Varnish (K) was prepared by mixing with stirring 100 g of the low-odorcrosslinkable compound (G) obtained in Example 8, 50 g of TE-2000 (apolybutadiene resin modified with methacrylic acid manufactured byNippon Soda Co., Ltd., Japan), 15 g of t-butyl perbenzoate, 0.3 g of 6%cobalt naphthenate and 0.008 g of hydroquinone.

EXAMPLE 13

Varnish (L) was prepared by mixing with stirring 230 g of the low-odorcrosslinkable compound (I) obtained in Example 10, 60 g of TE-2000, 60 gof B-1000 (a polybutadiene resin having a number average molecularweight of 1000, manufactured by Nippon Soda Co., Ltd., Japan), 150 g oflauryl methacylate, 5 g of t-butyl perbenzoate and 1 g of 6% cobaltnaphthenate.

EXAMPLE 14

Varnish (M) was prepared by mixing with stirring 100 g of the low-odorcrosslinkable compound (H) obtained in Example 9, 50 g of PS-203(unsaturated polyester resin modified with soya oil, resin content being98.7%, manufactured by Hitachi Chemical Co., Ltd.), 1.5 g of t-butylperbenzoate, 0.3 g of 6% cobalt naphthenate and 0.008 g of hydroquinone.

EXAMPLE 15

Varnish (N) was prepared by mixing with stirring 100 g of the low-odorcrosslinkable compound (J) obtained in Example 11, 50 g of TE-2000, 1.5g of t-butyl perbenzoate, 0.3 g of 6% cobalt naphthenate, and 0.008 g ofhydroquinone.

Properties of varnishes (K) to (N) obtained in Examples 12 to 15 andPS-202, a typical example of conventional unsaturated polyestervarnishes (a varnish of unsaturated polyester resin modified with soyaoil, manufactured by Hitachi Chemical Co., Ltd.), (Comparative Example),are listed in Table 2.

                                      TABLE 2                                     __________________________________________________________________________                 Example No.                                                                                           Comparative                                           12    13    14    15    Example *8                               __________________________________________________________________________    Varnish      Varnish K                                                                           Varnish L                                                                           Varnish M                                                                           Varnish N                                                                           PS-202                                         In the state of                                                                      Almost no                                                                           Almost no                                                                           Almost no                                                                           Almost no                                                                           Irritating                                     varnish                                                                              odor  odor  odor  odor  odor of                                                                       styrene                                  Odor                                                                                At drying *1                                                                         Slight                                                                              Slight                                                                              Slight                                                                              Slight                                                                              Strong                                                odor  odor  odor  odor  irritating                                                                    odor                                     Viscosity (at 25° C.)                                                  (poise) *2   10.9  8.0   13.5  12.1  1.8                                      Gel time (100° C., min.) *3                                                         8.2   9.1   6.2   7.3   8.5                                      Tensile strength                                                              (23° C., kg/mm.sup.2) *4                                                            0.3   0.03  0.2   0.4   0.3                                      Elongation (23° C., %) *4                                                           39    39    28    37    32                                       Adhesive strength under                                                       shear (23° C., kg) *5                                                               39    15    51    35    24                                       Volume resistivity                                                            (23° C., Ω-cm) *6                                                             3.2 × 10.sup.14                                                               2.5 × 10.sup.14                                                               1.5 × 10.sup.13                                                               1.9 × 10.sup.14                                                               2.0 × 10.sup.12                    Volatile content (%) *7                                                                    2.3   2.7   1.6   2.1   12.5                                     __________________________________________________________________________     Note                                                                          *1 A SAtype standard drier (450 × 350 × 350 mm) was kept at       120° C. and a tin container (100 × 100 × 20 mm)            containing 30 g of each varnish was placed in the drier for 30 minutes.       After that period, odor in the drier was judged with the nose.                *2 Viscosity was measured using a BLtype rotational viscometer.               *3 In a test tube with a diameter of 18 mm, a varnish was placed to the       height of 70 mm and the time required for gelation was measured by using      GE type gelation timer.                                                       *4 Measured according to JIS K6301.                                           *5 Using polyester coated copper wire with a diameter of 20 mm, a test        piece as shown in the attached drawings was made. The test piece was          coated with a varnish and cured at 120° C. for 3 hours to measure      tensile strength. FIG. 1 is a front view of the test piece and FIG. 2 is      crosssectional view of the test piece at a bound part. In the drawings, 1     is polyester coated copper wire with a diameter of 2.0 mm, 2 is bind line     with a diameter of 0.14 mm for biding the polyester coated copper wires,      and 3 is a bound part.                                                        *6 Using a resin plate of 20 mm thick and a ultrainsulation resistance        meter, volume resistivity was measured applying DC 500 V thereto.             *7 In a metal laboratory dish having a diameter of 60 mm, 10 g of a           varnish was placed and cured at 120° C. for 1 hour to measure          weight loss.                                                                  *8 As a curing agent, 1% by weight of benzoyl peroxide and as a curing        accelerator, 1% by weight of PT23 (manufactured by Hitachi Chemical Co.,      Ltd.) were used.                                                         

As is clear from Table 2, Varnishes K, L, M and N according to thisinvention are remarkably improved in odor both in the state of varnishand at drying comparing with the conventional unsaturated polyestervarnishes. Further volatile content of the varnishes of the presentinvention is as low as 1/4 or less of that of the conventionalunsaturated polyester varnishes. In addition, electrical and mechanicalproperties of the varnishes of the present invention are as high as orhigher than those of the conventional unsaturated polyester varnishes.

As mentioned above, there can be provided resin compositions which cansatisfy the requirements of prevention of environmental pollution andsaving resources and are suitable for producing reinforced plastics,paints and varnishes, adhesives, electrical parts, and the like.

What is claimed is:
 1. A crosslinkable compound obtained by reacting anaromatic hydrocarbon-formaldehyde resin with an α,β-unsaturatedmonocarboxylic acid or an ester thereof in the presence of anesterification or ester interchange catalyst.
 2. A crosslinkablecompound according to claim 1, wherein the α,β-unsaturatedmonocarboxylic acid or an ester thereof is used in an amount of 10 to200 parts by weight based on 100 parts by weight of the aromatichydrocarbon-formaldehyde resin.
 3. A crosslinkable compound according toclaim 1, wherein the aromatic hydrocarbon-formaldehyde resin isxylene-formaldehyde resin.
 4. A crosslinkable compound according toclaim 1, wherein the α,β-unsaturated monocarboxylic acid is acrylic acidor methacrylic acid.
 5. A crosslinkable compound according to claim 1,wherein the ester of α,β-unsaturated monocarboxylic acid is an alkylester of acrylic or methacrylic acid.
 6. A polymer obtained bypolymerization of a crosslinkable compound obtained by reacting anaromatic hydrocarbon-formaldehyde resin with an α,β-unsaturatedmonocarboxylic acid or an ester thereof in the presence of anesterification or ester interchange catalyst, the polymerization of thecrosslinkable compound being carried out by radical polymerization at alow temperature.
 7. A process for producing a polymer of thecrosslinkable compound obtained by reacting an aromatichydrocarbon-formaldehyde resin with an α,β-unsaturated monocarboxylicacid or an ester thereof in the presence of an esterification or esterinterchange catalyst, which comprises reacting said crosslinkablecompound at a temperature of from room temperature to 180° C., by usinga curing agent in an amount of 0.1 to 5% by weight and a curingaccelerator in an amount of 0 to 2% by weight, based on the weight ofthe crosslinkable compound.
 8. A crosslinkable compound according toclaim 1, wherein the aromatic hydrocarbon-formaldehyde resin isxylene-formaldehyde resin, toluene-formaldehyde resin,mesitylene-formaldehyde resin, durene-formaldehyde resin ornaphthalene-formaldehyde resin and the α,β-monocarboxylic acid isacrylic acid, methacrylic acid, α-chloroacrylic acid, or a crotonic acidand the alkyl ester contains from 1 to 4 carbon atoms in the alkylgroup.
 9. A crosslinkable compound according to claim 1, claim 2 orclaim 8, wherein the reaction of the aromatic hydrocarbon-formaldehyderesin with the α,β-unsaturated monocarboxylic acid or an ester thereofis effected at a temperature of 80° to 130° C.
 10. A polymer accordingto claim 6, wherein said radical polymerization is effected at atemperature of from room temperature to 180° C., in the presence of aperoxidic curing agent.